Electricity at 60 Hz is normally distributed by a 3 phase 11 KV or 33 KV network distribution network. Its final step is to pass through neighborhood transformers which drop the voltage down to typically either a nominal 110VΦ/N for use by the networks retail customers.
The AC Power distribution Network looking downstream behaves as a very low pass filter, i.e. it attenuates frequencies sharply much above 100 Hz and by 1400 Hz transmission at regulated voltages is all but impossible. This is primarily due to cumulative noise generated by all devices attached to the power network. Such electrical noise eventually swamps even the most sophisticated modulation schemes.
The design of power transformers with low downstream impedance (towards the load) and very high upstream impedance (towards source) is deliberate. In part to protect the medium and high voltage feeder networks from the very high composite noise that would otherwise be generated by all devices connected to the power reticulation network. As a result of this design characteristic, upstream message propagation is blocked. This makes the power distribution system difficult and expensive to use for bi-directional data networks such as Internet traffic.
AC Power is a commodity that can not be stored. In periods of high or low demand utility or power companies may use ‘Ripple Control’, a very low speed on/off semaphore messaging system, to signal control equipment located in the consumers meter-box. The utility uses this signal to control blocks of network load of the same type, i.e. to turn hot water heaters on and off during times of peak load.
The electricity supply company promises to provide electricity with a very high availability on ‘time of day’ and/or use based tariffs. Nominally amplitude variations of the AC signal are regulated to not exceed a fluctuation of +/−5% which may otherwise occur due to surge, disruption, sudden load spikes caused elsewhere in the network, or even the cumulative effect of AC motors in a large number of residential commercial and industrial appliances. Realizing the benefits to customers and themselves of providing off peak power, or ways of controlling load during times of peak demand, power companies use ‘Ripple Control’, currently operating under these regulatory constraints, to transmit their own control signals throughout the network. These signals normally are detected by sealed control relays in the customers meter box which result in turning off or on all ripple control relay circuits set to the transmitted code. Domestic and industrial uses include storage heating, hot water, and high loads such as Kilns and factory production lines that can easily be stopped and restarted if needed in emergencies. By offering a reduced tariff the electricity companies get to manage this load in times of emergency but can not easily isolate a single device or small customer.
Ripple Injection systems normally use short fixed duration bursts of a single frequency within a fixed 8 or 16 slot time window. The resulting ‘code’ is a binary number matched to a receiver controlling an on/off relay at all customer premises based normally on the type of controlled load.
Modern ripple injection systems based on a time division single frequency model.
Ripple injection messages are usually measured in signals per hour where each signal can typically take 6 to 12 seconds to transmit in effect 8 bits of data. This results in ripple control being useless as a general messaging system with its total throughput measured in bits per hour. The receivers are also bulky and expensive and not suited to the kind of automation that a customer would use.
Enermet is a major European manufacturer of ripple injection ‘plant’ that is used around the world. Current technology uses solid-state electronics devices matched to the distribution feeder voltage nominally at 11 KV, to add the ripple control signals. These devices can not operate continuously for prolonged periods due to overheating and have short life expectancies for a very expensive and functionally crucial device to the power company if they are used frequently.
The on/off duty cycle of existing ripple control systems is a significant design issue. Historically overheating and power consumption are the major factors limiting the equipment's use. Impedance mismatches and even the small voltage fluctuations at the high operating voltages of solid state ripple control result in the matching equipment overheating (low voltage) or needing to be rated at a high power to provide power in parallel with the main power distribution network (high voltage).
Existing ripple control equipment currently doesn't run much above a 1% utilisation due to over heating caused by the small voltages fluctuating between drawing and providing energy to a matched load typically in the 30 megawatt plus range.
Looking upstream the ‘reluctance’ of the network is extremely high. Designed that way to block the noise generated by all the devices attached to the network, from the feeder network itself. Consequently any upstream digital signal is blocked at each neighborhood transformer. IP over AC power-lines such as that used by “Adaptive Networks Inc.” therefore must include termination and retransmission at each neighborhood transformer. This requires expensive or elaborate devices or the co-location of data networking equipment to propagate the signal back to the central transmission point via other means such as radio, telephone line, fiber optic or such data line.
The problems continue downstream in distributing an IP type Internet network using the Power Network.
1. Cost. A high premium for a high bandwidth duplex signal with huge cost infrastructure for the upstream pathway. For example 14.4 kbps to 128 Kbps signal for IP type connectivity and demodulation of the signal at point of use. In England and the US recent trials used a $1000 device attached and sealed within the user/customer meter box as well as requiring upstream equipment and a telephone line at each neighborhood transformer.
2. Local distribution network. The meter box then requires connection to a local area network within the home typically using the telephone wires or other new wiring or wireless equipment to distribute the signal. Older buildings don't tend to have existing phone wiring in every room, and using an RF type link is expensive and restrictive based on building construction materials.
Adaptive Networks Inc. uses a spread spectrum approach to include modulated bandwidth that excludes interference. This other than complexity and cost also suffers limited distribution distance due to attenuation and interference.
Therefore, it is the object underlying the invention to provide an improved and/or secure low speed system for transmitting digital information via a power supply network and using this information to control and/or enhance electronic devices.
This object is solved by a transmission device for transmitting digital information via a power supply network, a receiving device for receiving digital information via a power supply network, a method for transmitting digital information via a power supply network, and a method for receiving digital information via a power supply network.
Therefore, a transmission device for transmitting digital information via a power supply network according to the present invention comprises                a generator for generating a simulated digital wave-form carrying the digital information to be transmitted, wherein the simulated digital wave-form is built of predetermined harmonic frequencies of a signal frequency, and        a high-voltage injector to inject the generated simulated digital wave-form carrying the digital information into the power supply network.        
Correspondingly, a receiving device for receiving digital information via a power supply network, according to the present invention comprises                an analog detector for detecting predetermined harmonic frequencies of a signal frequency, and        a logic device to output a logic signal corresponding to the output of the analog detector as said digital information.        
Further correspondingly, a method for transmitting digital information via a power supply network according to the present invention comprises the steps of:                generating a simulated digital wave-form carrying the digital information to be transmitted, wherein the simulated digital wave-form is built of predetermined harmonic frequencies of a signal frequency, and        injecting the generated simulated digital wave-form carrying the digital information into the power supply network.        
Still further correspondingly, a method for receiving digital information via a power supply network according to the present invention comprises the steps of:                detecting predetermined harmonic frequencies of the signal frequency, and        outputting a logic signal corresponding to the detection result as said digital information.        
Therewith, the present invention operates similarly to a ripple control system, at or below the same tolerances that existing ripple equipment operates. This is deliberate as incorporating these factors into the design reduces the certification requirements for deploying transmitters according to the present invention.
However, using the electrical characteristics of the AC network to design a matched transmitter and/or receiver according to the present invention, and knowing that any strange wave-form or combination of frequencies, or any type of modulation in our transmitter could be matched, the present invention took advantage of being able to produce a unique and specialized approach to signaling in the Power network, namely not to use expensive dynamic frequency splitting to increase the bit rate of a digital signal, but to seek robustness in using frequencies and minimal harmonics thereof emulating a digital signal not attenuated by the network and those not being interfered with by other electrical devices. Using only predetermined harmonics of the signaling frequency simplifies the detection circuitry and also minimizes interference created from the transmitter although generally only lower data throughput rates are achieved in comparison to the dynamic frequency splitting. The design and resulting circuit designs according to the present invention are extremely robust to give longevity and enable them to be embedded within the AC powered appliance's power supply.
The signal transmitted using the present invention will be detectable within the power supply of any electrical appliance or device connected to the AC power source. The present invention does not affect ripple control receivers or equipment attached to the power system.
The present invention does not address the bi-directional or IP markets, but transmits a proprietary modulation and data format. It is unidirectional and broadcast in nature unlike that used within power system based IP based (Internet) networks that have been tried to date. As set-out, the present invention is not simply the downstream piece of an IP based system. The present invention includes the physical integration to using only predetermined harmonics of the signaling frequency and through the possible and preferred use of cryptography techniques making an individual pathway between the transmitting device and a signal receiving device. The present invention thusly describes a much refined messaging system as it propagates freely anywhere there is an electrical power circuit, and without the need for other termination device or modifications to existing wiring.
Therewith, the signal transmitting device design according to the present invention maximizes the signals robustness at the receiving device interface according to the present invention based on being able to match exactly the electrical propagation characteristics of the transmission network to the programmable wave-form of the (high voltage) transmitter according to the present invention. The characteristics of the modulation and transmission according to the present invention include the following:                Low speed. Discrete Low frequencies, e.g. predetermined harmonics of a signaling frequency that itself is not a harmonic of the distribution frequency of the AC power network itself, e.g. 167 or 267 Hz.        Not needing to use Spread Spectrum or other sophisticated techniques, resulting in low cost and resistance to electrical noise.        No pulse shift keying as some ‘Ripple Control Systems’ do, and then only at a circuit level. The system according to the present invention improves data rate greatly by over 400% but still at a low speed of e.g. 400-2000 bits per second.        
In the transmission device according to the present invention, said high-voltage injector preferably comprises                drive stage transistors to inject the generated simulated digital wave-form carrying the digital information into the power supply network, and        a chopping unit that rapidly turns the drive stage transistors on and off in conformance with the shape of the low frequency wave-form, in particular at a frequency greater than 6 kHz but according to the fundamental signaling frequency to avoid a phenomenon common to digital signaling called ‘aliasing’.        
Correspondingly, the method for transmitting digital information via a power supply network according to the present invention preferably comprises the step of rapidly turning drive stage transistors on and off in conformance with the shape of the low frequency wave-form, in particular at a frequency greater than 6 kHz.
Where most modern solid state systems can not operate continuously due to heating and sizing constraints, this preferred embodiment according to the present invention offers a new system of rapidly switching the drive stage transistors, in the following referred to as ‘chopping’. Chopping involves rapidly turning the drive stage transistors on and off in conformance with the shape of the low frequency wave-form. Turning the transistors on and off at greater than 6 kHz, and being able to vary the message duty cycle based on the specific network condition, a nearly ‘100% on’ or signaling condition is approached. This also reduces the power rating of the injection device or any matching transformer connected to the power distribution network. This enables the system according to the present invention to ‘broadcast’ its digital signal continuously, at least as far as the receiver perceives it, and much more efficiently than used in other power transmission signaling systems. This preferred embodiment according to the present invention enables cooling the active system if required by altering the on/off or chopping duty cycle, or by reducing the message transmission rate down to a level to maintain just the date/time updates.
The chopping also reduces heating and the power consumption by around 50% transmitting actually only ½ the time and dramatically increasing the life expectancy of the equipment. In an electricity supply network the high frequency switching or chopping component is rapidly attenuated in the network within 1500 yards and is not seen by the receivers according to the present invention at all.
This preferred signal transmitting device design and preferred method for transmitting digital information via a power supply network improves a high voltage transmitter's power efficiency by more than 50%, achieving continuous transmission where other signaling transmission systems such as Ripple Control typically operate inefficiently at less than 1% utilization with a much lower effective data rate.
The transmission device according to the present invention further preferably comprises                a feedback control that detects specific conditions of the power supply network to vary the chopping on/off cycle of the drive stage transistors accordingly and/or to shut down and turn on the drive stage transistors accordingly.        
Correspondingly, the method for transmitting digital information via a power supply network according to the present invention further preferably comprises the steps of detecting specific conditions of the power supply network, and varying the chopping on/off cycle of the drive stage transistors accordingly and/or shutting down and turning on the drive stage transistors accordingly.
According to the present invention, i.e. for the transmission device, the receiving device, the method for transmitting digital information and the method for receiving digital information, said predetermined harmonic frequencies of the signal frequency preferably include the first and third harmonic frequencies of the signal frequency.
In this case, a logic ‘1’ might be defined as the primary signaling frequency and the negative cycle of the third harmonic at a predetermined first signal level, preferably −8 dB, and a logic ‘0’ might be defined as the negative cycle of the third harmonic at a predetermined second signal level, preferably −6 dB, preferably respectively preceded by a synchronization preamble at a higher frequency, preferably of some higher harmonic of the signal frequency.
According to the present invention, i.e. for the transmission device, the receiving device, the method for transmitting digital information and the method for receiving digital information, said digital information preferably is                date and/or time and/or time-zone information, and/or        control information, which control information is preferably encrypted and comprises an addressing functionality so that at least one particular receiving device, in particular one and only one particular receiving device, connected to said power supply network can access said control information, in particular control instructions and digital information attached thereto.        
In this case said digital information is preferably used                in a device or chip integrally adapted, by means of the circuit logic or design of said device or chip to process said digital information to control a remote activation or operation of some manufacturer feature or to enhance the device or chip by integration of a trusted control feature and/or an accurately synchronized date and time, and/or        for implementing secure remote instruction or operation of load management and switching devices used in high voltage power distribution systems.        
Further, according to the present invention said digital information might be used to transmit a synchronized date and time to update automatically and continuously a date and time to electrically powered devices using the power supply network for transmission.
Therewith, the control technology possible according to the present invention gives a power company the ability to easily securely and cheaply address a single customer's circuit, or a single appliance.
Preferred methods that will refer to uses of the system according to the present invention are:                1. Integration of Date and time into the display controller of a clock or control panel for an electrical appliance.        2. Integration of the time pulse into a PC Motherboard Real Time Controller Chip. This replaces the need for a battery on the motherboard and will allow time to be updated while the PC is connected. Therewith, cost of PC motherboard is reduced by removing need for battery backup by modification to the real time clock device such as represented by an Intel 8253 or SPK Electronics Taiwan RTC7301 or similar. Alternately, a device containing such RTC function such as an SMC Enhanced PCI South Bridge with real time clock can be directly connected to the receiver according to the present invention or have such a receiver integrated.        3. Secure remote control and load management of electrical switching equipment and load by power distribution companies. A mechanical device driven by hydraulic piston might activate an oil, air, vacuum, magnetic, sulfur hexafluoride, or other high voltage circuit breaker after the power has failed, to remove the load. Safety features to avoid mistakes might be included and the device might have a lock out so it is only activated on power loss or by specially regulated override control. A hydraulic activator activated after power failure might open its contacts and upon a programmable delay after power reinstatement will close the circuit breaker. This gives the companies a much more refined control of inductive load spikes upon trying to reinstate power. A particular control code might be reserved for electricity companies and the data field can include group addressing of devices.        4. Controlling electrical devices in the home by integrating securely addressed control information directly into appliance controller logic, e.g. in an autonomous house refrigerator, washing machine, DVD, or heater/air-conditioning system.        
The receiving device according to the present invention preferably comprises an optical interface arranged in an output path of the logic device. Such an optical isolation is used to protect attached digital devices from interference from or to the power supply.
The receiving device according to the present invention alternatively or additionally preferably comprises an information retrieval unit to retrieve control information directed to said particular receiving device.
Correspondingly, the method for receiving digital information via a power supply network according to the present invention preferably comprises the step of retrieving control information directed to said particular receiving device.
In the receiving device according to the present invention said information retrieval unit preferably comprises a decryption unit to verify whether or not said control information is addressed to said particular receiving device and to decrypt said control information with a predetermined key.
Correspondingly, the method for receiving digital information via a power supply network according to the present invention further preferably comprises the step of verifying whether or not said control information is addressed to a particular receiving device and to decrypt said control information with a predetermined key.
Therewith, the present invention preferably enables a method for transmitting control information using no explicit address.
The receiving device according to the present invention is preferably integrated in a personal computer or other electronic device displaying or using date and time or private control information or instructions.
Generally, it is preferred that the receiving device according to the present invention                outputs either a verified control signal or continuous date and time synchronized to an atomic source,        can be integrated into the controllers and integrated circuits providing an immediate and accurate date and time reference while the AC power is turned on,        generates a serial data stream output in a special format to minimise chip manufacturers development costs and directly connected to the manufacturers IC (the receiving device switches a digital signal of ones and zeroes built from the same DC voltage sources used by the appliance's electronic circuitry itself),        can be integrated at least partly into other devices such as Intel's or other manufacturers real time clock controller chip to reduce the cost of the PC motherboard or other device by removing the battery and associated units.        